Channel rank updates in multiple-input multiple-output communication systems

ABSTRACT

Embodiments of the disclosure provide a system and method for providing channel feedback information (CFI) from a user equipment device to a base station. CFI is transmitted from the user equipment device on first and second communication channels. The user equipment device is operable to measure the channel rank of a downlink channel and to select a preferred channel rank that is used to configure the CFI that is transmitted to the base station. The base station is operable to use the preferred channel rank to interpret the CFI transmitted by the user end device.

PRIORITY CLAIM

This application is a continuation of and claims the benefit of priorityfrom U.S. patent application Ser. No. 16/153,202, entitled “Channel RankUpdates in Multiple-Input Multiple-Output Communication System” andfiled on Oct. 5, 2018, which is a continuation of and claims the benefitof priority from U.S. patent application Ser. No. 15/664,346, entitled“Channel Rank Updates in Multiple-Input Multiple-Output CommunicationSystems” and filed on Jul. 31, 2017 (issued as U.S. Pat. No. 10,111,232on Oct. 23, 2018), which is a continuation of and claims the benefit ofpriority from U.S. patent application Ser. No. 14/830,917, entitled“Channel Rank Updates to Multiple-Input Multiple-Output CommunicationSystems” and filed on Aug. 20, 2015 (issued as U.S. Pat. No. 9,723,615on Aug. 1, 2017), which is a continuation of and claims the benefit ofpriority from U.S. patent application Ser. No. 14/147,911, entitled“Channel Rank Updates in Multiple-Input Multiple-Output CommunicationSystems” and filed on Jan. 6, 2014 (issued as U.S. Pat. No. 9,119,193 onAug. 25, 2015), which is a continuation of and claims the benefit ofpriority from U.S. patent application Ser. No. 12/891,160, entitled“Channel Rank Updates in Multiple-Input Multiple-Output CommunicationSystems” and filed on Sep. 27, 2010 (issued as U.S. Pat. No. 8,626,222on Jan. 7, 2014), which is a continuation of and claims the benefit ofpriority from U.S. patent application Ser. No. 12/053,577, entitled“Channel Rank Updates in Multiple-Input Multiple-Output CommunicationSystems” and filed on Mar. 22, 2008 (issued as U.S. Pat. No. 7,978,623on Jul. 12, 2011). Each of the above-referenced applications are fullyincorporated herein by reference in their respective entireties for allpurposes to the extent not inconsistent with this application.

The claims in the instant application are different than those of theparent application or other related applications. The Applicanttherefore rescinds any disclaimer of claim scope made in the parentapplication or any predecessor application in relation to the instantapplication. The Examiner is therefore advised that any such previousdisclaimer and the cited references that it was made to avoid, may needto be revisited. Further, any disclaimer made in the instant applicationshould not be read into or against the parent application or otherrelated applications.”

FIELD OF THE INVENTION

The present invention is directed in general to the field of informationprocessing. In one aspect, the present invention relates to a system andmethod for transmitting channel rank feedback information from one ormore user equipment devices.

DESCRIPTION OF THE RELATED ART

Wireless communication systems transmit and receive signals within adesignated electromagnetic frequency spectrum, but capacity of theelectromagnetic frequency spectrum is limited. As the demand forwireless communication systems continues to expand, there are increasingchallenges to improve spectrum usage efficiency. To improve thecommunication capacity of the systems while reducing the sensitivity ofthe systems to noise and interference and limiting the power of thetransmissions, a number of wireless communication techniques have beenproposed, such as Multiple Input Multiple Output (MIMO), which is atransmission method involving multiple transmit antennas and multiplereceive antennas. Such wireless communication systems are increasinglyused to distribute or “broadcast” audio and/or video signals (programs)to a number of recipients (“listeners” or “viewers”) that belong to alarge group. An example of such a wireless system is the 3GPP LTE (LongTerm Evolution) system depicted in FIG. 1, which schematicallyillustrates the architecture of an LTE wireless communication system 1.As depicted, the broadcast server 28 communicates through an EPC 26(Evolved Packet Core) which is connected to one or more access gateways(AGW) 22, 24 that control transceiver devices, 2, 4, 6, 8 whichcommunicate with the end user devices 10-15. In the LTE architecture,the transceiver devices 2, 4, 6, 8 may be implemented with basetransceiver stations (sometimes referred to herein as enhanced “Node-B”or “eNB” devices) which in turn are coupled to Radio Network Controllersor access gateway (AGW) devices 22, 24 which make up the UMTS radioaccess network (collectively referred to as the UMTS Terrestrial RadioAccess Network (UTRAN)). Each transceiver device 2, 4, 6, 8 includestransmit and receive circuitry that is used to communicate directly withany mobile end user(s) 10-15 located in each transceiver device'srespective cell region. Thus, transceiver device 2 includes a cellregion 3 having one or more sectors in which one or more mobile endusers 13, 14 are located. Similarly, transceiver device 4 includes acell region 5 having one or more sectors in which one or more mobile endusers 15 are located, transceiver device 6 includes a cell region 7having one or more sectors in which one or more mobile end users 10, 11are located, and transceiver device 8 includes a cell region 9 havingone or more sectors in which one or more mobile end users 12 arelocated. With the LTE architecture, the eNBs 2, 4, 6, 8 are connected byan S1 interface to the EPC 26, where the S1 interface supports amany-to-many relation between AGWs 22, 24 and the eNBs 2, 4, 6, 8.

As will be appreciated, each transceiver device, e.g., eNB 2, in thewireless communication system 1 includes a transmit antenna array andcommunicates with a user equipment device, e.g., user equipment (UE) 15,having a receive antenna array, where each antenna array includes one ormore antennas. The wireless communication system 1 may be any type ofwireless communication system, including but not limited to a MIMOsystem, SDMA system, CDMA system, SC-FDMA system, OFDMA system, OFDMsystem, etc. Of course, the user equipment devices, e.g., UE 15, canalso transmit signals which are received by the Node-B, e.g., eNB 2. Thesignals communicated between transmitter 102 and user equipment device104 can include voice, data, electronic mail, video, and other data,voice, and video signals.

Various transmission strategies require the Node-B to have some level ofknowledge concerning the channel response between the Node-B and eachuser equipment device, and are often referred to as “closed-loop”systems. An example application of closed-loop systems which exploitchannel-side information at the Node-B (transmitter) (“CSIT”) areprecoding systems, such as space division multiple access (SDMA), whichuse closed-loop systems to improve spectrum usage efficiency by applyingprecoding at the Node-B to take into account the transmission channelcharacteristics, thereby improving data rates and link reliability. SDMAbased methods have been adopted in several current emerging standardssuch as IEEE 802.16 and the 3rd Generation Partnership Project (3GPP)Long Term Evolution (LTE) platform. With such precoding systems, CSITcan be used with a variety of communication techniques to operate on thetransmit signal before transmitting from the transmit antenna array. Forexample, precoding techniques can provide a multi-mode beamformerfunction to optimally match the input signal on one side to the channelon the other side. In situations where channel conditions can beprovided to the Node-B, closed loop methods, such as MIMO precoding, canbe used. Precoding techniques may be used to decouple the transmitsignal into orthogonal spatial stream/beams, and additionally may beused to send more power along the beams where the channel is strong, butless or no power along the weak, thus enhancing system performance byimproving data rates and link reliability. In addition to multi-streamtransmission and power allocation techniques, adaptive modulation andcoding (AMC) techniques can use CSIT to operate on the transmit signalbefore transmission on the transmit array.

With conventional closed-loop MIMO systems, full broadband channelknowledge at the Node-B may be obtained by using uplink soundingtechniques (e.g., with Time Division Duplexing (TDD) systems).Alternatively, channel feedback techniques can be used with MIMO systems(e.g., with TDD or Frequency Division Duplexing (FDD) systems) to feedback channel information to the Node-B.

In the current LTE standard, channel quality information (CQI),precoding matrix index (PMI) and rank (collectively called channelfeedback information (CFI)) can be fed back from the UE to the Node-Busing one of two channels. One of the channels is the physical uplinkcontrol channel (PUCCH); the other channel is the physical uplink sharedchannel (PUSCH). The Node-B interprets CQI/PMI feedback transmitted oneach of these channels based on the rank feedback. However, the behaviorwith respect to rank is not specified for situations where CQI/PMIfeedback information is being transmitted on both the PUCCH and thePUSCH channels. For example, at various times, the rank indicated forfeedback information transmitted in the PUSCH channel may be differentthan the rank indicated for feedback information transmitted the PUCCHchannel. Currently there is no methodology to specify the behavior ofthe UE and Node-B for situations where rank indicated for feedbackinformation transmitted in the PUSCH channel is different than the rankindicated for feedback information transmitted the PUCCH channel.

Accordingly, an efficient feedback methodology is needed to providechannel feedback information to a Node-B using rank information. Inparticular there is a need for an improved system and method to specifythe behavior of the UE and Node-B for situations where rank indicatedfor feedback information transmitted in the PUSCH channel is differentthan the rank indicated for feedback information transmitted the PUCCHchannel. Further limitations and disadvantages of conventional processesand technologies will become apparent to one of skill in the art afterreviewing the remainder of the present application with reference to thedrawings and detailed description which follow.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be understood, and its numerous objects,features and advantages obtained, when the following detaileddescription of a preferred embodiment is considered in conjunction withthe following drawings, in which:

FIG. 1 schematically illustrates the architecture of an LTE wirelesscommunication system;

FIG. 2 depicts a wireless communication system in which one or more userequipment devices feed back information to a Node-B station for use inscheduling or otherwise precoding signal transmissions by the Node-Bstation;

FIG. 3 is an illustration of the simultaneous transmission of channelfeedback information on PUCCH and PUSCH channels in accordance with oneembodiment of the invention;

FIG. 4 is a flowchart illustration of processing steps for providingchannel rank feedback information on first and second transmissionchannels wherein the channel ranks on the two channels are dependent;

FIG. 5 is an illustration of the simultaneous transmission of channelfeedback information on PUCCH and PUSCH channels in accordance with analternate embodiment of the invention; and

FIG. 6 is a flowchart illustration of processing steps for providingchannel rank feedback information on first and second transmissionchannels wherein the channel ranks on the two channels are independent.

It will be appreciated that for simplicity and clarity of illustration,elements illustrated in the drawings have not necessarily been drawn toscale. For example, the dimensions of some of the elements areexaggerated relative to other elements for purposes of promoting andimproving clarity and understanding. Further, where consideredappropriate, reference numerals have been repeated among the drawings torepresent corresponding or analogous elements.

DETAILED DESCRIPTION

Embodiments of a system and methodology are disclosed for an efficientfeedback methodology to provide channel feedback information to a Node-Busing rank information. In particular, embodiments of the inventiondescribed herein provide an improved system and method to specify thebehavior of the UE and Node-B for situations where rank indicated forfeedback information transmitted in the PUSCH channel is different thanthe rank indicated for feedback information transmitted the PUCCHchannel. In various embodiments of the invention as described herein, achannel rank feedback report from the user equipment device will beunderstood to constitute a request by the user equipment device to use apredetermined channel rank.

Various illustrative embodiments of the present invention will now bedescribed in detail with reference to the accompanying figures. Whilevarious details are set forth in the following description, it will beappreciated that the present invention may be practiced without thesespecific details, and that numerous implementation-specific decisionsmay be made to the invention described herein to achieve the devicedesigner's specific goals. For example, selected aspects are shown inblock diagram form, rather than in detail, in order to avoid limiting orobscuring the present invention. In addition, some portions of thedetailed descriptions provided herein are presented in terms ofalgorithms or operations on data within a computer memory. Suchdescriptions and representations are used by those skilled in the art todescribe and convey the substance of their work to others skilled in theart. Various illustrative embodiments of the present invention will nowbe described in detail below with reference to the figures.

FIG. 2 depicts a wireless communication system 200 in which a Node-Bstation 202 communicates with one or more user equipment devices 204.i.With reference to the LTE wireless system depicted in FIG. 1, the Node-B202 may represent any of the control transceiver devices, 2, 4, 6, 8which act as a base station, while the user equipment device 204.i mayrepresent any of the end user devices 10-15. In the system 200 depictedin FIG. 2, one or more user equipment devices 206.i transmits channelfeedback information, including channel rank, over PUSCH channel 215 andPUCCH channel 216 to a Node-B station 202 for use in scheduling orotherwise precoding signal transmissions by the Node-B station 202. Atthe Node-B 202, the channel feedback information is decoded and the rankis extracted and is used to configure or adapt one or more input signalsthat are transmitted from a Node-B 202 (e.g., a base station) to one ormore user equipment devices 206.1-m (e.g., subscriber stations). As willbe appreciated, the Node-B station 202 and/or user equipment devices206.i include a processor, software executed by the processor, and otherhardware that allow the processes used for communication and any otherfunctions performed by the Node-B station 202 and each of user equipmentdevices 206.i. It will also be appreciated that the Node-B station 202can both transmit signals (over the downlink path) and receive signals(over the uplink path), and that each user equipment device 204.i canreceive signals (over the downlink path) and transmit signals (over theuplink path).

The Node-B 202 includes an array 228 of one or more antennas forcommunicating with the user equipment devices 206.1 through 206.m, eachof which includes an array 209.i having one or more antennas forcommunicating with the Node-B 202. In operation, a data signal s_(i)presented at the Node-B 202 for transmission to the user equipmentdevice 204.i is transformed by the signal processor 226.i into atransmission signal, represented by the vector x_(i). The signalstransmitted from the transmit antenna 228 propagate through a matrixchannel H_(i) and are received by the receive antennas 209.i where theyare represented by the vector y_(i). For a MIMO channel from the Node-B202 to the i^(th) user equipment device 206.i, the channel is denoted byH_(i), i∈{1, 2, . . . , m}. The channel matrix Hi may be represented asa k_(i)×N matrix of complex entries representing the complexcoefficients of the transmission channel between each transmit-receiveantenna pair, where N represents the number of transmit antennas in thetransmit antenna array 228, and k_(i) represents the number of antennasof the i^(th) user equipment device 206.i. At the user equipment device206.i, the signal processing unit 205.i processes the y_(i) signalsreceived on the k antennas to obtain a data signal, z_(i), which is anestimate of the transmitted data s_(i). The processing of the receivedy_(i) signals may include combining the yi signals with appropriatecombining vector information v_(i) retrieved from the codebook 207.i orotherwise computed by the user equipment device's signal processing unit205.i.

Precoding for downlink transmissions (Node-B to user equipment device)may be implemented by having each user equipment device 206.i determineits MIMO channel matrix Hi—which specifies the profile of thetransmission channel between a Node-B and an ith user equipmentdevice—in the channel estimation signal processing unit 205.i. Forexample, in a MIMO implementation, each user equipment device 206.1-mdetermines its MIMO channel matrix Hi by using pilot estimation orsounding techniques to determine or estimate the coefficients of thechannel matrix Hi. Each user equipment device 206.i uses the estimatedMIMO channel matrix or other channel-related information (which can bechannel coefficients or channel statistics or their functions, such as aprecoder, a beamforming vector or a modulation order) to generateprecoding information, such as precoding and power allocation values,appropriate for the MIMO channel matrix. This may be done by using thechannel-related information to access a precoder stored in the userequipment device codebook 207.i. In addition, each user equipment device206.i uses the estimated MIMO channel matrix or other channel-relatedinformation to generate channel rank information that is to be used toconfigure/adapt the signals transmitted by the Node-B.

In one embodiment, the channel rank report generator 201.i may includelogic and/or circuitry for detecting a change in the mode of operationof the user equipment device 206.i (e.g., from a single-antenna mode ofoperation to a multi-antenna mode of operation) so that channel rankinformation is generated and reported to the Node-B 202 only when such amode change is detected. The channel estimation/signal processing unit205.is operable to monitor a downlink channel to obtain measurements ofa plurality of channel parameters, including CQI, PMI and channel rank.A preferred rank is then selected for formatting CFI reports that aretransmitted to the Node-B on a plurality of communication channels,e.g., a PUSCH and a PUCCH. In various embodiments of the invention, theCFI, including channel rank, may be fed back to the Node-B either atperiodic time intervals or aperiodically. Furthermore, in variousembodiments of the invention, the CFI, including channel rank, may befed back to the Node-B in response to a request from the Node-B; or theCFI, including the channel rank, may be fed back to the Node-Bautonomously by the user equipment device based on predeterminedcriteria.

Rather than feeding back the full channel rank representation, the userequipment device 206.i may use a codebook 207.i to compress or quantizethe transmission profile (e.g., channel rank information) that isgenerated from the detected channel information and that can be used bythe Node-B in controlling signal transmission to the user equipmentdevice. The channel rank estimator 203.i generates aquantization/codebook index by accessing the user equipment devicecodebook 207.i which stores an indexed set of possible transmissionprofiles and/or channel matrices H_(i) along with associated channelrank information so that the estimated channel matrix information 204.igenerated by the signal processing unit 205.i can be used by the channelrank estimator 203.i to retrieve a codebook index from the codebook207.i. The output of the channel rank estimator 203.i is provided to achannel rank report generator 201.i that is operable to independentlydecide when to generate and feedback channel rank reports. For example,the channel rank report generator 201.i may include a channel ranktransition detector that detects a change in the channel rankinformation that meets a predetermined change threshold requirement sothat channel rank information is generated and reported to the Node-B202 via the feedback channel 215 only when the predetermined changethreshold requirement is met. In another example, the channel rankreport generator 201.i may include logic and/or circuitry for detectinga change in the mode of operation of the user equipment device 206.i(e.g., from a single-antenna mode of operation to a multi-antenna modeof operation) so that channel rank information is generated and reportedto the Node-B 202 only when such a mode change is detected.

The channel feedback information is transmitted via the PUSCH channel215 and the PUCCH channel 216 to the Node-B 202 where it may be storedand/or processed by the channel rank report detector/decoder 220. Forexample, a memory controller (not shown) in the channel rank reportdetector/decoder 220 may be used to update the previously reportedchannel rank information, either directly or using channel rankinformation retrieved from the codebook 222. In this way, the channelrank report detector/decoder 220 is operable to process the generatedchannel rank information to provide channel rank information that can beused by scheduling module 224 and AMC selection module 225 to generatescheduling or AMC information, respectively, for a particular userequipment device 206.i. As will be appreciated, the scheduling module224 may be used to dynamically control which time/frequency resourcesare allocated to a certain user equipment device 206.i at a given time.Downlink control signaling informs each user equipment device 206.i whatresources and respective transmission formats have been allocated. Thescheduling module 224 can instantaneously choose the best multiplexingstrategy from the available methods (e.g., frequency localized orfrequency distributed transmission). The flexibility in selectingresource blocks and multiplexing users will influence the availablescheduling performance.

In general, embodiments of the invention pertain to communicationsystems in which the user end device feeds back CFI, including CQI, PMIand rank, in at least two modes of feedback which may be over twological channels. In some embodiments of the invention the channel rankreported on each of the channels is interdependent and in someembodiments the ranks are the same. In other embodiments of theinvention, the channel rank reported on the two channels is independentand, therefore, the two channels can have different channel ranks.

For example in one embodiment, the first logical channel, e.g., thePUCCH, is configured to feed back wideband CFI to be used for schedulingdown link control information while the second logical channel, e.g.,the PUSCH, is configured to feed back frequency selective CFI to be usedfor scheduling down link data. In this case, the rank feedback on thesetwo reports are configured to be independent.

In another embodiment, the first logical channel, e.g., the PUCCH, isconfigured to feed back frequency selective CFI of a first type whichmay be used for scheduling down link data information while the secondlogical channel, e.g., the PUSCH, is configured to feed back frequencyselective CFI of a second type which may be used for scheduling downlink data. In this case, the rank feedbacks of these two reports areconfigured to be dependent. In this embodiment, it is possible that therank observed by the user equipment device in the first set of CFI isdifferent than the rank observed in the second set of CFI, in which casethe user equipment device will select rank observed in the first set ofCFI or the second set of CFI to be used for CFI reports on bothchannels. In one embodiment, the user equipment device may select thelower of the ranks of the two CFI sets as the choice of rank for boththe feedback CFI sets.

FIG. 3 is an illustration of the simultaneous transmission of channelfeedback information on a PUSCH channel 215 and a PUCCH channel 216 inaccordance with one embodiment of the invention wherein the channelranks on the two channels are dependent, i.e., set to be equal. The CFItransmitted on the PUCCH channel 216 is transmitted in a series ofsubframes with CQI and PMI information being transmitted together, withchannel rank being transmitted in a separate subframe at predeterminedintervals. For purposes of illustration, the CFI transmitted on thePUCCH channel 216 is shown to have a rank=1 at time t1. At time t2,however, the CFI transmitted on the PUSCH channel 215 is shown to have arank=2. As will be understood by those of skill in the art, however, thecurrent LTE standard does not provide a protocol for arbitrating betweenranks when the rank is different for CFI transmitted on the PUSCH 215and the PUCCH 216. In this embodiment of the invention, the rankreported on the two channels are interdependent on each other, i.e., atany time after a change in rank for either channel is detected, theranks on the two CFI reporting modes on the PUSCH and PUCCH areidentical. The user end device measures the rank for the two CFI reportsand thereafter then the user end will choose a preferred rank toconfigure both the CFI reports. Thus, the latest preferred rank reportedby CFI subframes either on the PUSCH or the PUCCH is used to interpretthe CQI/PMI report on the PUCCH. Therefore, in this embodiment of theinvention, the subsequently transmitted subframes 302 are processedusing a rank=2.

To ensure reliability of the rank report on the PUCCH 216, the rankreported on the PUSCH 215 should be nearly as reliable or more reliablethan the rank reported on the PUCCH 216. Also, since the rank andCQI/PMI reports are made on the same subframe on the PUSCH channel 215,the rank reported on the PUSCH 215 should be used to interpret theCQI/PMI on the PUSCH 215.

FIG. 4 is a flowchart illustration of processing steps for providingchannel rank feedback information on first and second transmissionchannels wherein the preferred channel ranks on the two channels aredependent. In step 402, the channel rank on a down link channel ismonitored to generate first and second sets of measured channel rank. Instep 404 a test is conducted to determine whether there has been achange in the measured channel rank of either of the first and secondsets of measured channel rank. If the result of the test conducted instep 404 indicates that either of the measured channel ranks haschanged, processing proceeds to step 406 wherein processing logicselects a preferred channel rank for formatting CFI reports on the firstand second channels. Processing then proceeds to step 408, wherein thepreferred channel rank is used to select the format for CFI reportstransmitted on the first and second communication channels. Referringagain to step 404, if the result of the test conducted in step 404indicates that there is no change in the measured channel rank on thefirst and second channels, processing proceeds to step 410 wherein thecurrent rank is used to select the format for CFI reports transmitted onthe first and second transmission channels.

In some embodiments of the invention, rank updates on the two channelsmay be independent of each other, i.e., the rank reported on the PUSCHmay be different than the rank reported on the PUCCH—this allowsdifferent CFI feedbacks to co-exist on the two channels. As an example,if the PUCCH has wideband CFI feedback and the PUSCH has user equipmentdevice-selected CFI feedback, then the ranks for these two cases can bedifferent. This implies that the rank reported on the PUSCH does notaffect the CQI/PMI reported on the PUCCH; likewise the rank reported onthe PUCCH does not affect the CQI/PMI reported on the PUSCH.

FIG. 5 is an illustration of the simultaneous transmission of channelfeedback information on PUCCH and PUSCH channels in accordance with analternate embodiment of the invention wherein the channel ranks for thetwo channels are independent. Again, for purposes of illustration, theCFI transmitted on the PUCCH channel 216 is shown to have a rank=1 attime t1. At time t2, however, the CFI transmitted on the PUSCH channel215 is shown to have a rank=2. In this embodiment of the invention,ranks reported on the two channels are not dependent on each other,i.e., at any instant of time, the rank on the two CFI reporting modes onthe PUSCH and PUCCH may not be identical. Thus, the latest rank reportedby CFI subframes on the PUSCH is used to interpret the CQI/PMI report onthe PUSCH and the latest rank reported by CFI subframes on the PUCCH isused to interpret the CQI/PMI report on the PUCCH. Therefore, in thisembodiment of the invention, the subsequently transmitted subframes 302are processed using a rank=1.

FIG. 6 is a flowchart illustration of processing steps for providingchannel rank feedback information on first and second transmissionchannels wherein the channel ranks on the two channels are independent.In step 602, the measured channel rank on a downlink channel ismonitored and first and second sets of measured channel rank aregenerated therefrom. In step 604 a test is conducted to determinewhether there has been a change in the measured channel rank on thefirst set of measured channel rank. If the measured channel rank on thefirst channel rank has changed, processing proceeds to step 606 and anew channel rank is used to select the format for CFI reportstransmitted on the first communication. If, however, the test conductedin step 604 indicates that the measured channel rank on the firstchannel has not changed, processing proceeds to step 608 where a test isconducted to determine whether there has been a change in the measuredchannel rank of the second channel. If the measured channel rank on thesecond channel has changed, processing proceeds to step 610 and a newchannel rank is used to select the format for transmitting CFI reportson the second channel communication channel. If, however, the testconducted in step 608 indicates that the measured channel rank on thesecond channel has not changed, processing proceeds to step 612 wherethe current channel ranks for the first and second channels are used toselect formats for transmitting CFI reports on the first and secondchannels, respectively.

In another alternate embodiment, CFI is interpreted using channel ranksthat are dependent (i.e., the same) during some reporting time intervalsand are independent (i.e., not forced to be the same) in other reportingtime intervals. For example in a first reporting time interval, T1, thePUCCH can be configured for wideband CFI (to be used for scheduling downlink control channel), while the PUSCH is configured for frequencyselective CFI (to be used for scheduling down link data). During thisreporting time interval, T1, channel ranks are independent. In anotherreporting time interval, e.g., T2, the PUCCH may be configured forfrequency selective CFI (e.g., type 1, to be used for scheduling a downlink data channel) while the PUSCH may be configured for frequencyselective CFI (e.g., type 2, to be used for scheduling down link data).During this reporting time interval, T2, channel ranks are dependent. Inthis alternate embodiment, the Node B can semi-statically (over aplurality of predetermined reporting time intervals) configure the CFIreporting to work in the dependent or independent modes. In an alternateembodiment, the CFI reporting can be chosen to work in the dependent orindependent modes as a function of the combination of the two CFIreporting types. For example, a parameter table may be established apriori by the user equipment device and the Node-B to provide parametersthat specify the CFI reporting mode, i.e., dependent or independentmode, based on the combination of CFI reporting types. The exactreporting mode used during a predetermined time interval will thendepend on the CFI reporting types over the two channels configured bythe Node-B.

By now it should be appreciated that there has been disclosed a systemand method for providing channel feedback information to a Node-B usingrank information. In one aspect of the invention, a method comprises:receiving a first set channel feedback information (CFI), including afirst rank report, from a user equipment device on a first communicationchannel; receiving a second set of CFI, including a second rank report,from the user equipment device on a second communication channel;comparing the first and second rank reports to determine the most recentrank report; and using the most recent rank report to interpret CFIreports. In an embodiment of the invention, the first set of CFI istransmitted on a physical uplink shared channel (PUSCH). In anotherembodiment of the invention, the second communication channel is aphysical uplink control channel (PUCCH).

In another aspect of the invention the method comprises: receiving afirst set of CFI, including a first rank report, from a user equipmentdevice on a first communication channel; receiving a second set of CFI,including a second rank report, from the user equipment device on asecond communication channel; using the first rank report to interpretthe CFI transmitted using the first communication channel; and using thesecond rank report to interpret the CFI transmitted using the secondcommunication channel.

In yet another aspect of the invention, a base station transceiver isprovided, wherein the base station transceiver comprises: a channelfeedback information report decoder operable to receive a first CFIreport, including a first rank report, from a user equipment device on afirst communication channel, to receive a second set of CFI, including asecond rank report, from the user equipment device on a secondcommunication channel, and further operable to compare the first andsecond rank reports to determine the most recent rank report; andprocessing logic operable to use the most recent rank report tointerpret CFI reports.

In yet another aspect of the invention a base station transceiver isprovided, wherein the transceiver comprises: a channel feedbackinformation report decoder operable to receive a first CFI report,including a first rank report, from a user equipment device on a firstcommunication channel, to receive a second set of CFI, including asecond rank report, from the user equipment device on a secondcommunication channel, and processing logic operable to use the firstrank report to interpret the CFI transmitted using the firstcommunication channel and use the second rank report to interpret theCFI transmitted using the second communication channel.

The methods and systems for an efficient feedback methodology to providechannel feedback information to a Node-B using rank information, asshown and described herein, may be implemented in software stored on acomputer-readable medium and executed as a computer program on a generalpurpose or special purpose computer to perform certain tasks. For ahardware implementation, the elements used to perform various signalprocessing steps at the Node-B (e.g., coding and modulating the data,precoding the modulated signals, preconditioning the precoded signals,extracting channel rank reports from the uplink messages and so on)and/or at the receiver (e.g., recovering the transmitted signals,demodulating and decoding the recovered signals, detecting changes inthe user equipment device state that require feedback of channel-sideinformation and so on) may be implemented within one or more applicationspecific integrated circuits (ASICs), digital signal processors (DSPs),digital signal processing devices (DSPDs), programmable logic devices(PLDs), field programmable gate arrays (FPGAs), processors, controllers,micro-controllers, microprocessors, other electronic units designed toperform the functions described herein, or a combination thereof. Inaddition or in the alternative, a software implementation may be used,whereby some or all of the signal processing steps at each of the Node-Band user equipment device may be implemented with modules (e.g.,procedures, functions, and so on) that perform the functions describedherein. It will be appreciated that the separation of functionality intomodules is for illustrative purposes, and alternative embodiments maymerge the functionality of multiple software modules into a singlemodule or may impose an alternate decomposition of functionality ofmodules. In any software implementation, the software code may beexecuted by a processor or controller, with the code and any underlyingor processed data being stored in any machine-readable orcomputer-readable storage medium, such as an on-board or external memoryunit.

Although the described exemplary embodiments disclosed herein aredirected to various feedback systems and methods for using same, thepresent invention is not necessarily limited to the example embodimentsillustrated herein. For example, various embodiments of a channel rankfeedback system and methodology disclosed herein may be implemented inconnection with various proprietary or wireless communication standards,such as IEEE 802.16e, 3GPP-LTE, DVB and other multi-user systems, suchas wireless MIMO systems, though channel rank information can also beused in non-MIMO communication systems. Thus, the particular embodimentsdisclosed above are illustrative only and should not be taken aslimitations upon the present invention, as the invention may be modifiedand practiced in different but equivalent manners apparent to thoseskilled in the art having the benefit of the teachings herein.Accordingly, the foregoing description is not intended to limit theinvention to the particular form set forth, but on the contrary, isintended to cover such alternatives, modifications and equivalents asmay be included within the spirit and scope of the invention as definedby the appended claims so that those skilled in the art shouldunderstand that they can make various changes, substitutions andalterations without departing from the spirit and scope of the inventionin its broadest form.

Benefits, other advantages, and solutions to problems have beendescribed above with regard to specific embodiments. However, thebenefits, advantages, solutions to problems, and any element(s) that maycause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeature or element of any or all the claims. As used herein, the terms“comprises,” “comprising,” or any other variation thereof, are intendedto cover a non-exclusive inclusion, such that a process, method,article, or apparatus that comprises a list of elements does not includeonly those elements but may include other elements not expressly listedor inherent to such process, method, article, or apparatus.

What is claimed is:
 1. A method, comprising: receiving, by a basestation via a first communication channel, a periodic channel feedbackinformation (CFI) report that is generated based on a first measuredrank; receiving, by the base station via a second communication channel,an aperiodic CFI report that is generated based on a second measuredrank; selecting one of the first measured rank or the second measuredrank based on respective values of the first and second measured ranks;and processing one or more subsequent CFI reports based on the selectedrank.
 2. The method of claim 1, wherein the selecting includes selectingthe one of the first measured rank or the second measured rank having alesser value.
 3. The method of claim 1, wherein the selecting is basedon whether the measured rank is frequency selective or wide band.
 4. Themethod of claim 1, wherein the first measured rank is frequencyselective.
 5. The method of claim 4, wherein the second measured rank iswideband.
 6. The method of claim 1, further comprising: processing oneor more subsequent CFI reports based on different ranks in response tooperating in an independent mode of operation.
 7. The method of claim 1,wherein the periodic and aperiodic CFI reports are formatted based onthe respective first and second measured ranks.
 8. The method of claim1, wherein the first communication channel is a physical uplink controlchannel (PUCCH) and the second communication channel is a physicaluplink shared channel (PUSCH).
 9. An apparatus, comprising: one or moreprocessors configured to: receive, via a first communication channel, aperiodic channel feedback information (CFI) report that is generatedbased on a first measured rank; receive, via a second communicationchannel, an aperiodic CFI report that is generated based on a secondmeasured rank; select, one of the first measured rank or the secondmeasured rank based on respective values of the first and secondmeasured ranks; and process one or more subsequent CFI reports based onthe selected rank.
 10. The apparatus of claim 9, wherein the apparatusis a cellular base station that includes one or more wireless radios andone or more antennas configured to receive the periodic CFI report andthe aperiodic CFI report.
 11. The apparatus of claim 9, wherein theapparatus is configured to select the one of the first measured rank orthe second measured rank having a lesser value.
 12. The apparatus ofclaim 9, wherein the apparatus is configured to select the one of thefirst measured rank or the second measured rank based on whether themeasured rank is frequency selective or wide band.
 13. The apparatus ofclaim 9, wherein the apparatus is configured to process one or moresubsequent CFI reports based on different ranks in response to operatingin an independent mode of operation.
 14. The apparatus of claim 9,wherein the periodic and aperiodic CFI reports are formatted based onthe respective first and second measured ranks.
 15. The apparatus ofclaim 9, wherein the first communication channel is a physical uplinkcontrol channel (PUCCH) and the second communication channel is aphysical uplink shared channel (PUSCH).
 16. A non-transitorycomputer-readable medium having instructions stored thereon that areexecutable by a computing device to perform operations comprising:receiving, via a first communication channel, a periodic channelfeedback information (CFI) report that is generated based on a firstmeasured rank; receiving, via a second communication channel, anaperiodic CFI report that is generated based on a second measured rank;selecting one of the first measured rank or the second measured rankbased on respective values of the first and second measured ranks; andprocessing one or more subsequent CFI reports based on the selectedrank.
 17. The non-transitory computer-readable medium of claim 16,wherein the selecting includes selecting the one of the first measuredrank or the second measured rank having a lesser value.
 18. Thenon-transitory computer-readable medium of claim 16, wherein theselecting is based on whether the measured rank is frequency selectiveor wide band.
 19. The non-transitory computer-readable medium of claim16, further comprising: processing one or more subsequent CFI reportsbased on different ranks in response to operating in an independent modeof operation.